Check out this MXR Phase 99! It's a stereo phaser that that has two different controls for your two channels. This pedal also works as a splitter if you wanted to run your signal to two different amps or channels. The phaser effect does not have to be turned on to split to two different channels. It also works and sounds great in the mono setting. This pedal works great and is no longer in production and considered a legacy product.

Check out what MXR has to say:

The Phase 99 combines two Phase 90 circuits in a single housing with Modern/Vintage, Series/Parallel, and Sync switches for ultimate phaser experimentation.

The Phase 90 sits with the Cry Baby® Wah Wah and the Fuzz Face® Distortion as one of the truly iconic effect pedals in music history, setting the standard by which all others in its category are judged. For years, experimental players have used two Phase 90 pedals side by side to create amazing textures from the way the two circuits interact with one another. Now, you can access the same sounds in a single pedal. 

The MXR Custom Shop Phase 99 opens up the sonic palette of the iconic Phase 90 by combining two phase circuits into a single Phase 90-sized housing. Separate rate controls for each circuit allow you to create intense complex phasing, and a Vintage switch toggles between modern and vintage style phasing. Further, the Phase 99 features a P/S switch to toggle signal flow between the circuits from series to parallel, and a Sync switch to synchronize the rate of each